Frequency-modulation phonograph pickup system



L. A. GOULD FREQUENCY-MODULATION PHONOGRAPH PICKUP SYSTEM May 11, 1948.

Filed Jan. 17, 1941 3mm leiiz'e 71. fioula Patented May 11, 1948 FREQUENCY-MODULATION PHONOGRAPH PICKUP SYSTEM Leslie A. Gould, Bridgeport, Conn., assignor, by

direct and mesne assignments, to Maguire Industries, Incorporated, a corporation of New York Application January 17, 1941, Serial No. 374,898

1 Claim. 1

This invention relates to new and useful improvements in sound reproducing apparatus and has particular relation to a pick-up device for use in the reproducing of sound from phonograph records.

The objects and. advantages of the invention will become apparent from a consideration of the following detailed description taken in connection with the accompanying drawing wherein a satisfactory embodiment of the invention is shown. However, it is to be understood that the invention is not limited to the details disclosed but includes all such variations and modifications as fall within the spirit of the invention and the scope of the appended claim.

In the drawing- Fig. 1 is a longitudinal sectional view through a pivotally mounted. arm of a pick-up and showing the invention;

Fig. 2 is a view on a larger scale and taken as looking downwardly on the forward portion of the arm the top wall of the latter being omitted; Fig. 3 is a transverse sectional view taken as along the line 33 of Fig. 1 and on an enlarged scale; and

Fig. 4 shows the wiring diagram.

The pick-up arrangement of the present invention is'adapted for use in connection with radio receiving sets and while particularly adapted for use with a frequency modulated set may also be used in connection with the usual amplitude modulated type of set. The device of the invention may be wired to a receiving set or it may be used to broadcast signals to such set for reception and reproduction by the latter when properly tuned.

Referring in detail to the accompanying drawing at is generally indicated the housing or casing of the arm and the same functions as a shield as will later more fully appear. Housing It) includes an upper elongated but transversely U-shaped sheet metal member and a somewhat similarly shaped lower member designated I l and [2 respectively.

These members are fitted together by disposing the open side of the bottom member [2 in the open side of the top member ll whereby the arm or housing comprises top and bottom walls l3 and M respectively and double thickness side walls [5 and I6 respectively. Secured to the member 12 is a post ll which depends from the arm or housing and comprises a portion of a means by which the arm may be pivotally mounted whereby'a stylus carried by the arm may follow the sound groove of a record and be fed across the record in the usual manner during reproduction.

A pivotal connection l'la provides for tilting of the arm relative to the post whereby the forward end of the arm may be raised off a record as will be understood. Within the forward portion of the arm I0 2. pair of brackets it carried by the arm member H support a clamp means comprising a pair of parts is and Zll which between them mount rubber bearing means 2! supporting an oscillatory stylus bar 22. This bar and the mentioned clamp including the plates i9 and 25 receive a reproducing stylus 23 and through the outer end of the bar is a tapped opening threadly receiving a clamping screw 24 by means of which the stylus is clamped firmly in place and which may be readily loosened to permit of replacement of a used stylus.

Stylus bar 22 projects rearwardly beyond the clamping plates I9 and 20 and on its projecting portion carries a closed coil 25 in the form of a ring although it will be appreciated that instead of the single turn shown the coil 25 might be of two or more turns if so desired.

Ring 25 is located in alignment with an end of a radio frequency coil 26. The ring is mounted with one edge on the stylus bar and such edge is so placed with respect to the coil 26 that as the ring is rockedback and forth (as the stylus bar is oscillated due to movement imparted to the stylus by the record groove) the ring is rocked bringing it more or less into the field of the coil thereby varying its inductance and wave length although not changing or varying the amount of current passing through the coil.

Mounted in a socket 21a in the rear portion of the arm H), although not necessarily so mounted, is a radio tube 21 shown more particularly in Fig. 4 as including the grid 28, the cathode 29, the plate 30 and the filament 3|. Tube 21 being mounted as described it may be conveniently replaced when that becomes necessary. Also in the arm is a variable condenser 32 adapted to be adjusted as by means of the screw 33 insulated from the condenser by a knob 34. There is also included a fixed or variable condenser 35 and a combined grid leak and fixed condenser 36 the purpose of which parts will be set forth.

Referring now to the wiring diagram of Fig. 4 as Well as to Fig. 1 it is noted that the coil 26 is placed in circuit with the variable condenser 32 as by the wires 31 and 38 of which the former is tapped to the condenser by a connection 39 and is also connected with the condenser 35 by a connection 40 and with the grid leak and condenser 36 as well as the grid 28 of the tube 21. A tap 4| connects wire 38 with the fixed plate of condenser 32 and a tap 42 grounds said wire on the arm or housing 10.

Condenser 35 is located in the antenna wire 43 which may be used in broadcasting by the pickup or which may be connected directly with the antenna connection of the radio receiving set with which the pick-up is used. A second wire 44 from the coil is connected with the cathode 29 and it will be seen in Fig. 4 that in this way'a radio frequency reaction or oscillation is set up between the two portions of the radio frequency coil. Thus the structure shown is an electron is particularly adapted for use with frequency modulated receiving sets it may also be used with amplitude modulated sets in which latter case the set is tuned slight off of resonance. If desired the device of the invention may be wired directly to the receiving set in which case the antenna wire 43 is connected directly with the antenna connection of the set or with the intermediate radio frequency transformer 49 in a superheterodyne set 56 and the condenser 35 may be adjusted if necessary.

As the stylus bar 22 is oscillated due to movement imparted to the stylus while operating in a sound groove the ring 25 is moved more into and out of the field of the coil 25 thereby varying its inductance and changing the wave length or frequency of the coil circuit. The movements of the do not-result in any variation in the amount of current being passed.

Having thus set forth the nature of my invention, what I claim is:

Aradio-phonograph comprising an impedance varying record pick-up, a superheterodyne radio circuit including a local oscillator having a tunable grid to cathode circuit, said tunable circuit including an inductance and a condenser and a circuit connectin vthe impedance varying pick-up in shunt to said condenser for effecting a frequency modulationzof the oscillatory current of said oscillator upon variation in the impedance of said pick-up.

ESLIE A. GOULD.

SITED The following references are ofrecord in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,689,564 Thorington Oct. 39, 1928 2,033,479 Murphy Mar. 10, 1936 2,112,810 Brimberg Mar. 22, 1938 2,115,917 Shanck May 3, 1938 FOREIGN PATENTS Number Country Date 373,973 Great Britain Dec. 31, 1932 

